Hi Lautrec,
This gave me idea on what eventually worked.
What I used a variation of what you have and the command sequence from
First updated without full cl-update
# cl-update --sync-only && emerge -1O python:3.9 && emerge -1O glibc && emerge -1O portage
then followed the editing /etc/locale.gen and /etc/env.d/02locale
editing /etc/locale.gen - (AU is my locale, adjust the locale for your location)
en_AU.UTF-8 UTF-8
editing /etc/env.d/02locale
LC_COLLATE="C"
LC_ALL=""
updated locale and checked result
# locale-gen
# locale -a
C
C.utf8
POSIX
en_AU.utf8
to finally get a clean cl-update running!
thank you!